Differential pressure switch with hinged plate on diaphragm

ABSTRACT

A pressure-responsive switch responsive to a differential pressure developed internally of a housing having a pressureresponsive diaphragm. The diaphragm supports an actuating element that impinges upon an axially displaceable pin extending outwardly of the housing. The pin bears against a flat spring that is flexed to close an electrical contact in dependence upon the pressure differential. The flat spring is removably mounted for exchange of springs to vary the range of operation of the switch.

United States Patent [1 1 [111 3,852,547

Dietz i Dec. 3, 1974 DIFFERENTIAL PRESSURE SWITCH WITH HINGED PLATE ON DIAPHRAGM [76] Inventor: Henry G. Dietz, 8O Salisburg Ave.,

Garden City, NY. 11530 [22] Filed: Aug. 24, 1973 [21] Appl. No.: 391,052

52 us. Cl. 200/83 Y, 200/83 A [51] Int. Cl. H0111 35/34 [58] Field Of Search ZOO/61.25, 81.9 R, 83 A, 200/83 8,83 N, 83 S, 83 SA, 83 Y, 83 P [56] References Cited UNITED STATES PATENTS 2,500,457 3/1950 Hess u 200/83 A 3,002,064 9/1961 Nelsen 200/83 A 3,005,887 10/1961 Robson 200/83 A 3,256,045 6/1966 $161261 ZOO/81.9 R

3,424,883 1/1969 Heskett ZOO/81.9 R 3,689,719 9/1972 Phillips 200/83 N FOREIGN PATENTS OR APPLICATIONS 676,140 2/l930 France 200/83 N Primary ExaminerRobert K. Schaefer Assistant ExaminerGerald P. Tolin Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [57] ABSTRACT 7 Claims, 5 Drawing Figures of no.1;

FIG. 3 is a section view taken along section line 3-3 DIFFERENTIAL PRESSURE SWITCH WITH HINGED PLATE ON DIAPHRAGM BACKGROUND OF THE INVENTION This invention relates generally to electrical switches and more particularly to an electrical differential pressure switch.

Differential pressure switches are known. Generally these switches are somewhat expensive to construct since they must be sealed to provide a positive seal on the vacuum side thereof and require leverage systems for rendering them sensitive. They are not able to take large overloads without damage and are substantially limited as to range of operation so that if a wide range of response to pressures is desired there is a decided limitation as to this range. Furthermore, the switches are generally circular in configuration and they require special complex tooling for the manufacture thereof.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide a sensitive electrical differential pressure switch which is,

inexpensive to construct and easy to 'vary the sensitivity thereof and which has a very wide range pressure response. It has a minimum of working parts and has the abilityto obtain large leverage ratios. Another object of the present invention isto provide an electrical differential pressure switch of a configuration which makes it possible to construct various sizes of the switch for different applications without great tooling costs. V

Another object of the present invention is to provide a switch which is readily sealed eliminating the use of friction-creating seals. 1

BRIEF DESCRIPTION OF THE-DRAWINGS Other features and advantages of the electrical differential pressure switch in accordance with the present invention will be better'understood as described in the following specificationv and appended claims in conjunction with- -the following drawings in which:

to the invention;

FIG. 2 is a se'ction view taken along section line2 2 FIG. 1 is a front elevation view of a switch accordingofFlG. 2; I

FIG. 4 is a fragmentary section -view of a modification of the switch in FIGSYI and 3 and illustrates a flowswitchembodiment; and i I FIG. 5 is a section view taken along section line 5-,-5.

A v prises a front plate and a back plate 12 spaced from each other by rectangular gaskets 14,15 made of a compressible material, such as cork or the like, and

held together by a plurality of screws 17 within busha diaphragm 20 made of a flexible material; for example cloth suitably impregnated with butyl or silicone, and a diaphragm pressure plate 21a which comprises a tongue of a metallic frame 21. The plate 21a is actually not a part of the frame 2l'and the cloth diaphragm 20 is bonded thereto as illustrated in FIGS. 2 and 3. The diaphragm pressure plate 21a is constructed with lesser surface area than the cloth diaphragm 20 and has an edge 23 bearing on an edge surface 24 of the frame 21 so that it is pivotal thereon so that the two opposed edges 23, 24 define a hinge or pivot for pivoting of the backing or pressure plate 210. The assembled diaphragm and backing plate define a vacuum space 26 and a pressure space 27 within a housing 10, 12 of the electrical differential pressure switch according to the invention.

A bracket 29 is mounted on the front plate 10 and supports thereon a micro switch having an electrical contact 31 bearing against a flexible flat clock spring 33 mounted on the bracket by a threaded fastener 34 and its nut 34a. I

A floating pin 36 provided with a head 36a, of larger diameter. than the shank of the pin, is axially movable in a bearing 40 mounted on the bracket 29. The pin 36 extends through the bearing into the vacuum space 26. A seal 42 seals the base of the bearing and opening in the front plate through which the pin 36 passes and forms a seal circumferentially of'the floating pin and .provided on the backside of the switch and is in communication'with theinterior of the pressure space 27. Both compartments are fluidtight. i

In operation a vacuum is supplied to the space 26and fluid pressure is supplied to the pressure space 27. The differential pressure willactuate the floating pin which bears on the flat clock spring 33 which will flex and actuate the" micro switch contact. The differential pressure switch can be actuated by air flow, a liquid level of pressure, alevel-of granulematerials or pressure from an inflated bladder subjected to externalpressure and is excellent for use with fluidic circuits. 1

When used as a differential pressureswitch it can be ures the, total pressure and the vacuum connector is connected to an opening in an airduct perpendicular to the air flow (static pressure). It can accordingly be used 'to indicate staticpressu're and it can alsoindicate a vacuum.

The switch construction according to the the invention allows increasing the 'size of the switches conings 18. Between the front andback' plates is mounted structed and increasing the area of the diaphragm so that the sensitivity of the switch can be increased. A sensitivity of 0.02 inches of water column pressurehas been obtained. Likewise, by decreasing the area of the diaphragm the switch can be used at high pressures, in

pounds per square inch levels.

The use of a diaphragm with a backing plate construction and the hinge position and direct pin actuation at a pointvery close to the hinge point results in a possibilityof using a small diaphragm to seal the vacuum side of the switch with no friction loss in transmitting the main diaphragm force to the micro switch. This makes the switch totally sealed on the vacuum side and makes use of friction-creating seals unncessary.

Moreover, the flat spring can be removed and changed and accordingly a different pressure response can be set on the switch by changing the flat spring.

.A modification of the switch is shown in FIGS. 4 and Sin which the diaphragm 21a is provided with an eyeleted'hole 22. This embodiment makes the switch a flow switch. The fluid media, which could include water or some other liquid, passing th'rougli the pressure connection into the inner chamber of the switch would pass through the eyeleted hole and out thevacuum connection of the switch. The pressure in the pressure chamber would be higher than the pressure in-the vacuum chamber. The difference between these two pressures is dependent on the rate of flow of the fluid through the eyeleted hole. This difference in pressure can be established to actuate the micro switch when a specific rate of flow is obtained.

What l claim and desire to secure by letters patent is:

fining a hinge for said pressure plate about which the pressure plate pivots, an electrical contact mounted on saidhousing exteriorly of said space, an actuator for'ac:

tuating said contact to an operative position comprising a flexible flat spring mounted exteriorly of said casing for flexing to a position to close said contact, an axially displaceable pin in communication with the interior of said housing and extending outwardly thereof for bearing against said float spring to deflect it in a direction for closing said contact, an actuating element mounted on said diaphragm for movement therewith to contact and engage said pin to actuate it in response to a pressure differential in said compartments flexing the diaphragm in a direction for actuating said switch, and connectors for applying a medium to one of said compartments to develop said differential pressure.

2. An electrical differential pressure switch accord ing to claim 1, in which said diaphragm comprises a rectangular flexible area, said diaphragm pressure plate having a generally rectangular area of lesser dimension than the area of. said flexible'material.

3. An electrical differential pressure switch according to claim 1, in which said actuating element is disposed adjacent said diaphragm pressure'plate edge surface.

4. An electrical differentiaal pressure switch according to claim 3, in which said actuating element comprises an adjustingscrew, one of said plates having a sealed opening defining an access to .said adjusting screw, and means sealing said opening.

5. An electrical differentialv pressure switch according to claim 1, including means removably mounting said flat spring for interchangementfof flat springs of different strengths therebyto vary the response of said switch to different pressure differentialsu,

- 6. A differential pressure switch according to claim 1, including a thin flexible seal circumferentially of said contact flexing when the contact is actuated? 7. A differential pressure switch according to claim whereby said differentialiswitch'functions as'a flow switch actuatable when a specific flow rate obtains -40 through said opening. 

1. A differential pressure switch comprising a housing comprising two spaced, opposed plates defining a fluidtight space therebetween, a flexible pressure responsive diaphragm comprising a flexible material and a diaphragm pressure plate bonded to said flexible material separating said space into two compartments, a rigid member having an edge surface in said space opposed to an edge surface of said pressure plate and in close proximity therewith, the edge surfaces jointly defining a hinge for said pressure plate about which the pressure plate pivots, an electrical contact mounted on said housing exteriorly of said space, an actuator for actuating said contact to an operative position comprising a flexible flat spring mounted exteriorly of said casing for flexing to a position to close said contact, an axially displaceable pin in communication with the interior of said housing and extending outwardly thereof for bearing against said float spring to deflect it in a direction for closing said contact, an actuating element mounted on said diaphragm for movement therewith to contact and engage said pin to actuate it in response to a pressure differential in said compartments flexing the diaphragm in a direction for actuating said switch, and connectors for applying a medium to one of said compartments to develop said differential pressure.
 2. An electrical differential pressure switch according to claim 1, in which said diaphragm comprises a rectangular flexible area, said diaphragm pressure plate having a generally rectangular area of lesser dimension than the area of said flexible material.
 3. An electrical differential pressure switch according to claim 1, in which said actuating element is disposed adjacent said diaphragm pressure plate edge surface.
 4. An electrical differentiaal pressure switch according to claim 3, in which said actuating element comprises an adjusting screw, one of said plates having a sealed opening defining an access to said adjusting screw, and means sealing said opening.
 5. An electrical differential pressure switch according to claim 1, including means removably mounting said flat spring for interchangement of flat springs of different strengths thereby to vary the response of said switch to different pressure differentials.
 6. A differential pressure switch according to claim 1, including a thin flexible seal circumferentially of said contact flexing when the contact is actuated.
 7. A differential pressure switch according to claim 1, in which said diaphragm has an opening providing communication between said two compartments, whereby said differential switch functions as a flow switch actuatable when a specific flow rate obtains through said opening. 